The same camera appears to show a man on his way to carry out the attack after leaving the property.

The person in the CCTV footage can be seen carrying a Lidl bag at 6.50am on Friday morning, just 90 minutes prior to the attack on the District Line train.

Ian Harvey, leader of Spelthorne Council, said: “Clearly there should now be an independent inquiry about the actions of all relevant agencies to ascertain exactly what has been going on.”

The Joneses are believed to have fostered the 18-year-old three years ago.

A second man, a 21-year-old Syrian named as Yahya Faroukh, was also arrested and is believed to have been under care of the Joneses at one time.

According to MailOnline, the 18-year-old is thought to have been a “problematic foster child” who arrived in the the UK aged 15.

The bomb failed to explode fully but passengers were left injured by a fireball inside the train (Rex)

Here’s everything we know so far about the Parsons Green terror attack (PA)

A source said: “Both Penny and Ron were finding them difficult to deal with. [A] friend said she doesn’t know if it was over extremism but Penny referred it to the authorities. They decided these were going to be the last two students they had.”

On Saturday, pesidents in Cavendish Road were forced to evacuate as police raided the address Jones address.

The pair were awarded MBEs in 2009 for services to children and families. It is believed they have fostered up to 300 children over 40 years.

A neighbour described them as “beautiful people”, with one calling them “great pillars of the community”.

“They do a job that not many people do,” they added.

On Sunday the UK’s terror threat level was downgraded from critical to severe, meaning an attack is highly likely.

Yahya Faroukh, a 21-year-old Syrian, has also been arrested (Facebook)